Metadata determines treatment of content by automated systems, including “user generated content” web sites. The metadata may be conveyed with the content or may be determined by other techniques, including systems based on digital watermarking or content fingerprinting. In some arrangements, treatment depends on the temporal length of a content excerpt that matches a pre-existing work. In others, treatment depends on popularity—either of the content, or a pre-existing work from which it was derived. A great variety of other factors and contexts can also be considered. Automated tools to preliminarily identify possible “fair use” can be realized; further determination may be made by human evaluators (including crowd-source approaches).